5fps vs 10fps w/ USB1 webcam

[galacticphoto]

This post isn't really about software, but may be of interest if you are still using a usb 1 webcam for planetary/lunar imaging.

A couple years ago, these was a look of discussion about preferred frame rates and gain settings for "best" webcam images. In short, over 5fps, or gain set over 25-30%, the image suffers. This must be traded off against the preference for more frames and better individual exposures.

I've attached a simple comparitive test showing the compression loss from a usb 1 webcam. First an expanded area (X3) from a single frame (frame 10 arbitrarily selected from the 100 frame sequences) from two sequences, 5fps (upper left), 10fps (upper right). Note the "larger" pixelization of the 10fps (this coarser "quantization" is due to compression, and represents a lower spatial frequency response).

Below those two, are the same area from the two raw stacks. No post processing.

Robert

[galacticphoto]

I forgot the attachment on the comparison...see below

Robert

[BT Technologies]

Excellent demonstration Robert. I know we have spoke about this on the phone last week and I wanted to try the lower frame rates like we discussed. In the past, I have always went with the "max" frame rate to get as many images in a given period of time possible. Now, by looking at your comparisons this was clearly the wrong way to go.

Great info Robert!!!!

Originally Posted by galacticphoto

I forgot the attachment on the comparison...see below

Robert

[Gary Beal]

Robert,
I agree, a great comp, and one which many have differing views on. I always thought that 5fps was as much as the USB system would work with, any more and you suffered compression and its associated artifacts. Correct?
Since you started this, any suggestions for a USB 2 camera, I am currently using an older Toucam 740, and am reasonably happy, but that doesn't mean I can't move with the times.
Thanks,
Gary

[galacticphoto]

Gary:

I guess that I should have posted this thread in the planetary section instead of the SW section, we're a bit off topic, but to answer your question, either Lumenera (USB2) or DMK (firewire), depending on your computer interface preference. The Point Grey cameras actually appear to be the best choice from a hardware perspective, but have minimal software support.

The Lumenera and DMK cams have several successful planetary/lunar/solar users. Both (640X480 models) run uncompressed at or above 30fps (the Lumenera goes to 60 w/o ROI, higher using ROI, if you have sufficient subject surface brightness; some planetary work requires exposure times that keep you at 30fps or less, some will let you run faster, most lunar can be done at the highest speed your cam can go). Stay with the 640X480 model (larger pixels) if you use a long FL scope, if you use a short FL scope, consider the slower, higher pixel count models (smaller pixels). Go with a monochrome model, and use a filter wheel. This will give you higher resolution (15 or 25% higher than the similar RGB cam, depending on the RGB debayering interpolation and information in the scene).

Lucam Recorder, arguably the most convenient/versatile webcam control program, supports only the Lumenera today (a real plus in choosing the Lumenera), but the developer has announced that he will have DMK support later this year (makes the choice more difficult).

Robert